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Mixing tank, MF-VOF and Species Transport - Divergence Error

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Old   September 11, 2018, 05:29
Default Mixing tank, MF-VOF and Species Transport - Divergence Error
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Soheil
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Hi,

I am trying to simulate fluid mixing inside a mixing tank with Multi-Fluid VOF model with Species transport. In a tank with height of 57 mm, is 40 mm water and 17 mm air at the top, which is applied by patching. Through an inlet (radius: 2 mm, length of the pipe: 20 mm, injection velocity: 1 m/s), Ethanol is injected to the system. Magnetic stirrer with 300 RPM.

Some General Details: Implicit Multi-Fluid VOF model + Species transport (no volumetric reaction), K-e realizable Standard Wall Function, transient mode, sliding mesh, pressure outlet at the top with value of for 1 backflow volume fraction for air, single PC parallel 4 cores.

I obtained the steady-state results by MRF and solving only the Flow and Turbulence equations, without injection of ethanol. Only air+water and MF-VOF model.
Used the results of steady-state for transient mode. After some time, almost 0.2 or 0.3 seconds in real-time, simulation stops with the error: floating point exception and sometimes huge value for continuty. (Some Pictures are Attached)

* By disabling species transport equation, simulation can continue but with species, it fails to run. I changed the URFs, disabled the energy equation for some time, added 0.999 for backflow and other combinations... but it FAILS!

** Same steady-state results with Air+water in transient mode, works fine. The issue is Addition of mass and injection, which I can not control it....

*** Short visualization video of the mixture volume fraction. [Dropbox Link]


Any advice is highly appreciated. It's really urgent!!
Attached Images
File Type: jpg errors.jpg (109.1 KB, 12 views)
File Type: png mixtureVolumeFraction.png (64.5 KB, 15 views)
File Type: png tankGeometry.png (67.4 KB, 10 views)
File Type: png meshFluent.png (58.3 KB, 8 views)
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